tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * efibc: control EFI bootloaders which obey LoaderEntryOneShot var
3 * Copyright (c) 2013-2016, Intel Corporation.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 */
14
15#define pr_fmt(fmt) "efibc: " fmt
16
17#include <linux/efi.h>
18#include <linux/module.h>
19#include <linux/reboot.h>
20#include <linux/slab.h>
21
22static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
23{
24 size_t i;
25
26 for (i = 0; i < strlen(str); i++)
27 str16[i] = str[i];
28
29 str16[i] = '\0';
30}
31
32static int efibc_set_variable(const char *name, const char *value)
33{
34 int ret;
35 efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
36 struct efivar_entry *entry;
37 size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
38
39 if (size > sizeof(entry->var.Data)) {
40 pr_err("value is too large (%zu bytes) for '%s' EFI variable\n", size, name);
41 return -EINVAL;
42 }
43
44 entry = kmalloc(sizeof(*entry), GFP_KERNEL);
45 if (!entry) {
46 pr_err("failed to allocate efivar entry for '%s' EFI variable\n", name);
47 return -ENOMEM;
48 }
49
50 efibc_str_to_str16(name, entry->var.VariableName);
51 efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
52 memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
53
54 ret = efivar_entry_set(entry,
55 EFI_VARIABLE_NON_VOLATILE
56 | EFI_VARIABLE_BOOTSERVICE_ACCESS
57 | EFI_VARIABLE_RUNTIME_ACCESS,
58 size, entry->var.Data, NULL);
59 if (ret)
60 pr_err("failed to set %s EFI variable: 0x%x\n",
61 name, ret);
62
63 kfree(entry);
64 return ret;
65}
66
67static int efibc_reboot_notifier_call(struct notifier_block *notifier,
68 unsigned long event, void *data)
69{
70 const char *reason = "shutdown";
71 int ret;
72
73 if (event == SYS_RESTART)
74 reason = "reboot";
75
76 ret = efibc_set_variable("LoaderEntryRebootReason", reason);
77 if (ret || !data)
78 return NOTIFY_DONE;
79
80 efibc_set_variable("LoaderEntryOneShot", (char *)data);
81
82 return NOTIFY_DONE;
83}
84
85static struct notifier_block efibc_reboot_notifier = {
86 .notifier_call = efibc_reboot_notifier_call,
87};
88
89static int __init efibc_init(void)
90{
91 int ret;
92
93 if (!efi_enabled(EFI_RUNTIME_SERVICES))
94 return -ENODEV;
95
96 ret = register_reboot_notifier(&efibc_reboot_notifier);
97 if (ret)
98 pr_err("unable to register reboot notifier\n");
99
100 return ret;
101}
102module_init(efibc_init);
103
104static void __exit efibc_exit(void)
105{
106 unregister_reboot_notifier(&efibc_reboot_notifier);
107}
108module_exit(efibc_exit);
109
110MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
111MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
112MODULE_DESCRIPTION("EFI Bootloader Control");
113MODULE_LICENSE("GPL v2");